Regional climate model of the Arctic atmosphere

Abstract

A regional climate model of the whole Arctic using the dynamical package of the High-Resolution Limited Area Model (HIRLAM) and the physical parameterizations of the Hamburg General Circulation Model (ECHAM3) has been applied to simulate the climate of the Arctic north of 65 øN at a 50-km horizontal resolution. The model has been forced by the European Centre for Medium-Range Weather Forecasts (ECMWF) analyses at the lateral boundaries and with climatological or actual observed sea surface temperatures and sea ice cover at the lower boundary. The results of simulating the Arctic climate of the troposphere and lower stratosphere for January 1991 and July 1990 have been described. In both months the model rather closely reproduces the observed monthly mean circulation. While the general spatial patterns of surface air temperature, mean sea level pressure, and geopotential are consistent with the ECMWF analyses, the model shows biases when the results are examined in detail. The largest biases appear during winter in the planetary boundary layer and at the surface. The underestimated vertical heat and humidity transport in the model indicates the necessity of improvements in the parameterizations of vertical transfer due to boundary layer processes. The tropospheric differences between model simulations and analyses decrease with increasing height. The temperature bias in the planetary boundary layer can be reduced by increasing the model sea ice thickness. The use of actual observed sea surface temperatures and sea ice cover leads only to small improvements of the model bias in comparison with climatological sea surface temperatures and sea ice cover. The validation of model computed geopotential, radiative fluxes, surface sensible and latent heat fluxes and clouds against selected station data shows deviations between model simulations and observations due to shortcomings of the model. This first validation indicates that improvements in the physical parameterization packages of radiation and in the description of sea ice thickness and sea ice fraction are necessary to reduce the model bias.

Albedo of coastal landfast sea ice in Prydz Bay, Antarctica: Observations and parameterization

“…The parameterization of Parkinson and Washington (1979) only considers broadband albedo for snow and bare ice (PW79). The Alfred Wegener Institute Regional Climate Model for the Arctic Region (Dethloff et al, 1996;HIRHAM) considers the dependence of albedo on surface temperature. The Arctic Regional Climate System Model (Lynch et al, 1995;ARCSYM) includes the impacts of snow thickness and ice thickness on the albedo.…”

Evaluation of snow/ice albedo parameterizations and their impacts on sea ice simulations

“…Adding one more layer of complexity, some parameterizations consider an albedo that varies with surface temperature. A model that parameterizes the albedo in this fashion is the Alfred Wegener Institute Regional Climate Model for the Arctic Region (Rinke, personal communication, 2004;Dethloff et al, 1996; hereafter referred to as HIRHAM). In addition to a dependence on the surface temperature, a few parameterizations include variations associated with snow depth and ice thickness.…”

Influence of changed vegetations fields on regional climate simulations in the Barents Sea Region

“…This includes a summary of available measurement stations from 1880 to 1990. Regional modelling studies have been performed by Lynch et al (1995Lynch et al ( , 2001Lynch et al ( , 2004, Dethloff et al (1996Dethloff et al ( , 2001 and Rinke et al (2006) for example.…”